So other than an over-the-counter purchase in past centuries, where does arsenic come from? Besides water? And volcanos emitting it into the air? Could Ross Poldark have realized that if he found copper then he'd also have an opportunity to sell the arsenic made from smelting?

When substances like copper are melted so they can be extracted from the rocks they're embedded in, it's possible to produce a dust residue. This residue has been referred to as the poudre de succession, a rather relaxed term for arsenic.

Tired of waiting for that inheritance? Reportedly some people sped up the process by adding a bit of almost tasteless white powder to the victims victuals. So, arsenic has been called the inheritance powder, and it's hard to separate fact from fiction because a confession would have led to a death sentence.

But because arsenic has preservative properties and also was used to control household pests with more than two legs, it was a source of revenue for miners.

The Botallack Mine near Cornwall, and a mine used in filming the original Poldark and some scenes of the latest version, did produce tin, copper and arsenic.

This could have added a whole new twist to the novel by Winston Graham, assuming it's not in the book.

So the next time I'm watching the latest episode of Poldark, and Aidan Turner gives that smoldering look, I might be wondering if he's thinking about his enemies and has a second reason for wanting to discover copper in the mine.